An ancient migration of elephants takes place in the dry season, between the Selous and Mozambique's Niassa Game Reserves. This is one of the largest natural trans-boundary eco-systems in Africa and at the last consensus it was estimated that 64,400 elephants roam the two parks, with 84% on the Tanzanian side.
Fierce tiger fish and smooth slippery vandu catfish are caught in the rivers. The latter is equipped with primitive lungs allowing it to cross land for short distance in an attempt to find water during the dry season.
The best time for visiting Selous is between June and November, the dry season when most of the wildlife can be seen along the rivers. Short rains start thereafter. From December to February is still good but it gets very hot and humid. January to April is good for viewing birdlife and glorious scenery but roads become impassable. Most camps are closed from April to May due to the heavy rains.